diminutive vertebral artery

Hi - I am a 29 yr old female with a history of coarctation of aorta, repaired 15 yrs ago. I also have a bicuspid aortic valve which is unrepaired.

I have been seeing a physical therapist for the past 3 months for a headache which won't go away! It's at the back of my head, at the base of skull.

About 2 weeks ago, during some neck rotations I nearly fainted. The physiast told me it's technical term was "vasovagal pre-syncope".

Anyway, to cut a long story short, I was sent for an MRA. The report states "The entire visualized left vertebral artery is developmentally diminutive and the corresponding right vertebral artery is developmentally dominant".

1. Could you explain the consequences of the above findings?

2. Also, does this explain my constant headaches?

I appreciate your assistance, thanks.